1. Field of the Invention
The present invention is directed to a separator for separating particulate matter from a fluid carrying medium. More particularly, the present invention is directed to a particulate matter carrying gas separator which is of an axisymmetrical configuration relative to the flow of the carrying gas in the separator.
2. Brief Description of the Prior Art
Devices for separating particulate matter carried in a gas have been known in the prior art for a long time. The particulate separators of the prior art include filters and electrostatic precipitators. A third category of prior art particulate separators work on the principle that when a carrying gas stream including particulate matter is forced to travel in a curved duct, the particles are affected to a larger extent by a resulting centrifugal force than the carrying gas. Consequently, the path of travel of the particles in the curved duct is different than that of the carrying gas, and therefore the particles may be captured and collected by appropriately positioned collecting slots or devices.
Several particle separators of different construction, but employing the above-noted principle, have been devised in the prior art and are widely used in the chemical and related industries and for purifying stack-gases and the like prior to their release into the environment. The prior art particle separators of the above-noted type are often referred to in the industry as "cyclone separators." Examples of cyclone separators may be found in U.S. Pat. Nos. 3,972,696; 3,710,561; 2,696,911; 2,468,607 and in British Patent Specification No. 570,578 and in German Pat. Nos,. 352,654 and 543,466.
A principal disadvantage of cyclone separators is their large size and their general inability to collect smaller than approximately 10 micron sized particles. However, as is well appreciated by those skilled in the art, present-day practice in the chemical and related industries and in the energy-producing field often requires removal of substantially all particulate matter from a carrying gas, including removal of particles in the 2-10 micron range.
In order to remove particulate matter smaller than 10 microns, the prior art principally utilizes electrostatic precipitators. Electrostatic precipitators, however, have a relatively high cost of initial construction, and while operating, require a relatively high input of energy.
As an alternative to electrostatic precipitators and in order to separate particles substantially in the 1-10 micron range, a particulate separator was devised which utilizes a shock wave created in a supersonic flow of a carrier gas to separate the particulate matter. This "supersonic velocity" separator is described in a report written by Hans D. Linhardt titled "Investigation of High Velocity Wedge Separator for Particle Removal in Coal Gasification Plants" and submitted to the U.S. Department of Energy under contract EF-77-C-01,2709.
U.S. Pat. No. 4,292,050 assigned to the same assignee as the present application for patent, discloses a particulate separator adapted for separating particles as small as approximately 1.0 micron by a combination of a curved duct and a shock zone in a supersonic gas flow. The patent also discloses the utilization of a curved duct in a fast, but less than supersonic flow (approximately 0.2-1.0 Mach) for collecting particles in the 1-10 micron range, and the utilizatition of a condensation phenomenon in a supersonic flow for capturing particles smaller than approximately 1.0 microns.
Although the high velocity separator disclosed in the above-noted report submitted to the U.S. Department of Energy, and in U.S. Pat. No. 4,292,050, function well, there is still a need in the prior art for an efficient separator adapted for removing approximately 2-10 micron sized particles from a carrying gas. This need exists particularly in light of the fact that a particulate separator operating with supersonic, or close to supersonic gas flow velocity may require higher than desirable energy input and fabrication of relatively delicate equipment.
A feature of the particle separator described in U.S. Pat. No. 4,292,050 is that the separator utilizes an elongated duct, which is curved in its elongate direction in order to impart a centrifugal force to the carrying gas and the therein contained particulate matter. Other embodiments of the separator disclosed in U.S. Pat. No. 4,292,050 as well as the separators described in the above-noted report submitted to the U.S. Department of Energy, comprise substantially straight elongated ducts containing a supersonic gas flow.
A common feature of all of the above discussed particular separators is that the separators are not axisymmetrical relative to the direction of the carrier gas flow, although a Technical Proposal to the Energy Research and Development Administration, U.S. Department of Energy, dated Aug. 5, 1977 mentions the possibility of constructing an axisymmetrical particulate separator which would utilize a cone rather than a wedge in a supersonic gas flow. An axisymmetrical separator employing a conical obstruction in the flow of gaseous potassium carrying liquid droplets of lithium metal is also suggested by D. G. Elliot in Technical Release No. 34-32 of the Jet Propulsion Laboratory, Sept. 20, 1960. In spite of the foregoing, the present inventors are unaware of any actual or suggested prior art particle separator which is axisymmetrical relative to the direction of the gas flow, and which utilizes a centrifugal force created by a wall of a duct for the separation of the particles.